Charter airline nightstops in Manchester at a hotel where the crew were given Do Not Disturb signs with a picture of an aeroplane on them. Of course, the hotel staff ignored these and hoovered noisily in the corridors.
One night we arrived at the hotel to check in, after a tiring day. I asked the girl on the desk for "one of those signs to hang on the door that says "Please hoover outside my door all day". She said "Ooh, we haven't got any signs like that." Reply: "I had one last time, it had a picture of an aeroplane on it." "Do you mean this?" (holding up an aircrew sign). "Yes, that's it." "It doesn't say: please hoover outside my door". "No, but that's the effect it has!"
Makes you feel better, sometimes, this sort of thing